Fig. 1. Dual polarity MALDI-MS spectra obtained from jejunal mucosal regions of the rat small intestinal tissue section. Total ion spectra of (a) negatively charged lipids including fatty acids (FA), cholesterol sulfate, taurocholic acid, ceramide phosphates (CerP), sphingomyelins (SM), phosphatidic acids (PA), phosphatidylethanolamines (PE), and phosphatidylinositols (PI) and (b) positively charged lipids including lysophosphatidylcholines (LPC) and phosphatidylcholines (PC) obtained on the same pixel points. * indicates matrix-derived oligomeric structural ion signals as previously described.20,21 Ions are [M ± H]^± unless indicated.